Enabling low-temperature processing of amorphous SiZnSnO thin-film transistors through combined Ar plasma treatment and annealing

초록

One of the critical factors in fabricating amorphous oxide thin-film transistors (AOS TFTs) is the annealing temperature. The a-SiZnSnO (a-SZTO) material exhibits excellent electrical properties and stability, comparable to the well-known a-InGaZnO material. However, a-SZTO requires a relatively high optimized annealing temperature of 500 degrees C. This high annealing temperature poses a challenge for applying a-SZTO to various substrates and applications. To reduce the annealing temperature of a-SZTO, a combined process of Ar plasma treatment and thermal annealing was proposed. When Ar plasma treatment was performed after thermal annealing, the a-SZTO TFT did not exhibit switching behavior, making transistor operation impossible. However, when thermal annealing was performed after Ar plasma treatment, the device demonstrated a high mobility of 24.05 cm2/Vs and a threshold voltage shift of 1.83 V after 7200 s of PBTS stress. In comparison, the device that underwent only thermal annealing at the same temperature exhibited a lower mobility of 18.56 cm2/Vs and a higher threshold voltage shift of 2.89 V. The increase in oxygen vacancies due to Ar plasma treatment acts as a defect within the thin film. However, during the thermal annealing process, the enhanced atomic mobility induced by thermal energy facilitates the reconfiguration of metal-oxygen bonds more effectively. Consequently, performing thermal annealing after Ar plasma treatment improves both the electrical properties and PBTS stability compared to thermal annealing alone. These results demonstrate that a-SZTO TFTs with performance comparable to those annealed at 500 degrees C can be fabricated by conducting thermal annealing at 350 degrees C after Ar plasma treatment. This approach overcomes the limitations of high-temperature processing and expands the applicability of a-SZTO to various substrates and applications.

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